I. Field of the Invention
The present invention relates generally to radio antennas and, more particularly, to high frequency Vivaldi antennas.
II. Description of Related Art
The Vivaldi antenna (essentially a tapered slot antenna) is a well-known radiator for ultra-wideband sensing and communications applications. This type of antenna is attractive because it is compact (low profile), light weight, and cost effective to fabricate, in addition to having relatively high directivity. Over the years, various topologies for the Vivaldi antenna have been developed. The three main classes include the cavity-based conventional Vivaldi antenna, the antipodal Vivaldi antenna, and the balanced-antipodal Vivaldi antenna. Each of these variants lass its own advantages and disadvantages. Compared to the antipodal implementation, it is expected that both the cavity-based and the balanced structures have lower cross-polarization interference effects. The cavity-based and balanced designs, however, are more complicated to fabricate due to the need to embed the feeding element (impedance transformer) within the substrate layer.
Variations of the above three Vivaldi classes also have been introduced, derived from either properly shaping the conductor geometry or modifying the substrate layer and dielectric composition, in order to further improve the radiation characteristics or miniaturize the structure. For example, slots or corrugated edges can be added to the flared sections of the antenna to achieve a more compact form factor, and a dielectric director can be embedded in the substrate to enhance the gain of the radiator.